In a wireless communication system, a signal at a transmitting end is usually a superposition of multiple signals. For example, in an Orthogonal Frequency Division Multiplexing (OFDM) system, the signal at the transmitting end is a superposition of multiple sub-carrier signals; in a Code Division Multiple Access (CDMA) system, the signal at the transmitting end is a superposition of multiple code word signals. This kind of signal composition leads to a high Peak Average Rate (PAR) of the signal. A mathematical definition of the PAR is:
  PAR  =      10    ⁢          log      (                        max          ⁢                                                                  s                ⁡                                  (                  t                  )                                                                    2                                    E          ⁡                      [                                                                            s                  ⁡                                      (                    t                    )                                                                              2                        ]                              )        ⁢          (              ⅆ        b            )      
where s(t) is a time domain signal; max(*) represents a maximum value; E[*] represents a mathematical expectation value.
A high PAR restricts the efficiency of a power amplifier and increase power consumption. Therefore, the PAR needs to be suppressed, and average transmission power of the signal may be improved through suppressing the PAR.
In the prior art, an amplitude limiting filter technology is adopted to suppress the PAR. A fixed amplitude threshold is selected, and all time domain values greater than the threshold are limited to the threshold value. Then out-of-band radiation power is limited through multiple times of filtering.
However, amplitude limiting not only improves the average power of transmitting the signal, but also introduces extra noise. If the selected amplitude threshold is too great, the effect of reducing the PAR is insignificant; if the selected amplitude threshold is too small, the introduced noise is increased, which leads to an increase in the probability of a signal receiving error. For example, for a signal of 64 Quadrature Amplitude Modulation (64 QAM) and 15/16 code rate, the signal may fail to be received correctly.